The formula
Monthly Bandwidth = Visitors × Pages Per Visit × Average Page Weight × (1 + Safety Buffer) Example: 10,000 visitors × 3 pages × 2.16MB × 1.20 = 78GB "Bandwidth" in a hosting context almost always means total monthly data transfer, not connection speed — how much data your server sends out to every visitor's browser over a billing period, added up. It scales directly with three things: how many people visit, how many pages each of them loads per visit, and how heavy each page is once every image, script, and font is counted.
How heavy is a typical web page?
This is the number most bandwidth estimates get wrong by guessing. HTTP Archive’s Web Almanac measures it directly by crawling millions of real sites. In the 2025 edition, the median mobile page weighs 2.16MB once every resource is counted, and the median desktop page 2.41MB.
Page weight also varies substantially by page type, which matters for a bandwidth estimate. A median mobile home page is 2.56MB, while a median mobile inner page — an article, a product, anything a visitor reaches after landing — is only 1.77MB. For a site where visitors typically continue beyond the homepage, using the home page figure for every page view can overestimate your transfer.
Mobile page weight has grown about 203% over the decade to July 2025 — roughly tripling — which is why estimates based on older figures can come out low.
| Percentile | Page Weight | Typical Site |
|---|---|---|
| P25 | ~1.1 MB | Lean, text-focused sites |
| P50 (median) | ~2.2 MB | Mobile web median |
| P75 | ~4.1 MB | Image galleries, product pages |
| P90 | ~8.3 MB | Video, heavy JavaScript bundles |
If you don't know your own site's actual weight, running it through a page-speed testing tool (Chrome DevTools' Network tab, PageSpeed Insights, or similar) will give you a measured page weight to use instead of a preset.
Why the safety buffer matters
Traffic doesn't arrive evenly across a month. A single viral post, a marketing campaign, or a seasonal spike can push a normal month's traffic well above its average, and most hosting bandwidth caps are hard limits per billing period, not soft averages. A 20–50% buffer on top of the raw calculation is common planning guidance precisely to absorb that variance without getting caught out by an overage fee or a throttled connection right when traffic is highest.
Frequently asked questions
How much bandwidth does a website need?
It depends on your traffic and page weight: multiply monthly visitors by pages per visit by average page size. A site with 10,000 monthly visitors, 3 pages per visit, and a typical 2.16MB page weight needs about 65GB of raw monthly transfer, or about 78GB with a 20% safety buffer.
What is the average web page size?
About 2.16MB on mobile and 2.41MB on desktop, per the 2025 HTTP Archive Web Almanac, which measures this by crawling millions of live websites. Home pages are heavier than inner pages — 2.56MB against 1.77MB on mobile — so a site whose visitors view several pages per visit transfers less per view than the headline figure suggests. Mobile page weight has roughly tripled over the past decade.
How much safety buffer should I add to my bandwidth estimate?
20–50% is common guidance, to absorb traffic spikes and growth over a billing period without hitting a hard cap. Sites with unpredictable traffic (news, viral content, seasonal sales) should lean toward the higher end.
References & Sources
- Page weight percentiles: HTTP Archive Web Almanac 2025 — Page Weight (published January 2026), based on crawling millions of live websites.